JP3567089B2 - Capacitive pressure sensor - Google Patents

Capacitive pressure sensor Download PDF

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Publication number
JP3567089B2
JP3567089B2 JP28906198A JP28906198A JP3567089B2 JP 3567089 B2 JP3567089 B2 JP 3567089B2 JP 28906198 A JP28906198 A JP 28906198A JP 28906198 A JP28906198 A JP 28906198A JP 3567089 B2 JP3567089 B2 JP 3567089B2
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Prior art keywords
capacitance
electrode
pressure sensor
semiconductor substrate
active
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JP2000121472A (en
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潤一 堀江
敦史 宮崎
智 嶋田
明彦 斉藤
保夫 小野瀬
範男 市川
恵二 半沢
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Hitachi Ltd
Hitachi Automotive Systems Engineering Co Ltd
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Hitachi Ltd
Hitachi Car Engineering Co Ltd
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Priority to JP28906198A priority Critical patent/JP3567089B2/en
Priority to DE19983646T priority patent/DE19983646B3/en
Priority to US09/807,325 priority patent/US6564643B1/en
Priority to PCT/JP1999/005116 priority patent/WO2000022397A1/en
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/0041—Transmitting or indicating the displacement of flexible diaphragms
    • G01L9/0072—Transmitting or indicating the displacement of flexible diaphragms using variations in capacitance
    • G01L9/0073—Transmitting or indicating the displacement of flexible diaphragms using variations in capacitance using a semiconductive diaphragm

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Fluid Pressure (AREA)
  • Pressure Sensors (AREA)

Description

【０００１】
【発明の属する技術分野】
本発明は流体の圧力を検出する圧力センサ、特に自動車のエンジン制御等に使用される半導体微細加工技術を利用した圧力センサに関する。
【０００２】
【従来の技術】
従来の圧力センサとしては、例えば特開平７−７１６２ 号に記載の圧力センサがある。
【０００３】
特開平７−７１６２ 号に記載の圧力センサは、周囲圧の変化に応じて変化することのない基準容量および周囲圧に応じて変化する感知容量を有し、半導体基板に形成した容量式の圧力センサであって、半導体基板に直接形成した拡散層である第一電極および所定の圧力に保たれるよう封止された空洞を介して第一電極と対面して形成した単結晶シリコンから成る導電領域を含む可撓性ダイアフラムの第二電極で構成される。基準容量，感知容量とも半導体基板に拡散層を形成しこれを第一電極として用いている。上記記載のセンサは、周囲圧力の変化により可撓性ダイアフラムが偏位して第一電極および第二電極間の容量が対応して変化することを特徴としている。
【０００４】
【発明が解決しようとする課題】
容量式圧力センサの高精度化をはかる方法として、圧力変化に関わらない加工ばらつきないしノイズ等の外乱要因によるアクティブ容量の特性変化をキャンセルする手段として、アクティブ容量とほぼ同程度の容量を有し周囲圧力によって実質的に変化しない基準電極を用い、検出回路で両者の容量変化の差分もしくは比をとる技術は従来から良く知られている。
【０００５】
半導体基板上に基準容量，アクティブ容量および検出回路を有する容量式圧力センサに関して高精度化をはかる際の課題は、基準容量−半導体基板間に基板不純物濃度ないし基板−基準容量電極の電位差に応じて変化する寄生容量（接合容量）が生じることである。このため半導体基板を接地または電源電圧として用いている検出回路と接続した場合、基準容量の電極間で形成する所定の容量に対し電極−半導体基板間の寄生容量が非常に大きくかつ変化し、アクティブ容量の変化量に対する寄生容量を含めた基準容量のＳＮ比が増大・変化し測定精度が低下するという課題がある。
本発明の目的は、基準容量−半導体基板間の寄生容量を小さくかつ電圧依存性を実質的に無視でき、測定精度が良い１チップの圧力センサを提供することにある。
【０００６】
【課題を解決するための手段】
上記目的は、半導体基板上に、周囲圧力に応じて変化するアクティブ容量，周囲圧力に対し実質的に変化しない基準容量，前記アクティブ容量および基準容量と電気的に接続され両者の差ないし比を検出し半導体基板の電位を利用して動作する回路を有し、前記基準容量が、前記半導体基板上に誘電体を介して設けられた導電性の電極によって形成され、前記半導体基板と前記回路とが接続された１チップの半導体容量式圧力センサによって達成される。
【０００７】
【発明の実施の形態】
本発明の第１実施例の断面図を図１に、平面図を図２に示す。
【０００８】
本実施例には、半導体基板１０に酸化物誘電体２０を介して形成したアクティブ容量１００および基準容量２００，検出回路３００から構成される半導体容量式圧力センサの圧力検出ＩＣ４００を示した。
【０００９】
半導体基板１０は半導体に一般的に用いられている単結晶シリコン基板である。バイポーラと比較してより少ない工程で高集積化できることで知られているＣ−ＭＯＳデバイスを用いる場合には、抵抗率８〜１２Ωｃｍ程度のｎ型またはｐ型単結晶ＣＺ基板を用いる。
【００１０】
酸化物誘電体２０は半導体基板１０とアクティブ容量１００および基準容量 ２００を半導体基板１０から電気的に絶縁している。酸化物誘電体２０は熱酸化膜，ＣＶＤ（Ｃｈｅｍｉｃａｌ Ｖａｐｏｒ Ｄｅｐｏｓｉｔｉｏｎ ）酸化膜、等で形成され比誘電率は３〜４程度である。Ｃ−ＭＯＳデバイスと同時形成する際には、熱酸化膜（フィールド酸化膜）を用いることが可能であり、工程数の低減につながるためより安価な圧力センサを提供することが出来る。
【００１１】
アクティブ容量１００はアクティブ容量固定電極３０ｂ，バリア誘電体層４０，空隙１１０，ダイアフラム構造体１２０で構成される。空隙１１０は封止用誘電体５０によりほぼ真空に気密封止されている。このため周囲圧力に比例してダイアフラム構造体１２０は変位する。ダイアフラム構造体１２０はアクティブ容量固定電極３０ｂと対面するダイアフラム電極１２０ａ部分と固定足場１２０ｂ部分からなる。ダイアフラム構造体１２０にポリシリコンを用い不純物拡散法などで導体化すればダイアフラム電極１２０ａを得ることが出来る。また固定足場１２０ｂは、空隙１１０を分離層エッチングにより作成する際にあらかじめ分離層をバリア誘電体層４０をエッチングストップ層として用い除去することによりバリア誘電体層４０を介して半導体基板１０に固定することが出来る。このような構成にすることにより、周囲圧力の変化をアクティブ容量固定電極３０ｂとダイアフラム電極１５０間の容量変化として変換することが可能である。アクティブ容量固定電極３０ｂおよびダイアフラム電極１５０の電位は下記の方法により検出回路３００に導くことが出来る。すなわち、ダイアフラム電極１５０の電位はダイアフラム電極接続部１３０により配線３０ｃ，コンタクト構造７０を経由して配線部６０ｂに導かれる（図１）。同様にアクティブ容量固定電極３０ｂも配線３０ｃ，コンタクト構造７０を経由し配線部６０ｂに達する（図２）。ダイアフラム電極接続部１３０は酸化物誘電体２０上に形成した配線３０ｃ上のバリア誘電体層４０の一部を除去することにより電気的な導通を得る構造である。下部電極３０ａ，アクティブ容量固定電極３０ｂ，配線３０ｃは導電性膜であり、不純物拡散したポリシリコン膜やシリサイド等のＣ−ＭＯＳデバイスのゲートと同時加工すると工程が簡略できより安価な圧力センサを提供できる。
【００１２】
基準容量２００は下部電極３０ａ，バリア誘電体層４０，上部電極６０ａから構成される。基準容量２００は酸化物誘電体２０を介して半導体基板１０上に形成する。このため半導体基板１０−下部電極３０ａ間で形成される寄生容量は従来例と比較して非常に小さくすることが可能となる。さらに半導体基板１０−下部電極３０ａ間の寄生容量は電圧依存性を実質的に有さない。従って測定精度の良い安定した圧力センサを提供することが出来る。
【００１３】
図８に本発明を適用した圧力センサのブロック線図を示す。本実施例は一般的なスイッチドキャパシタ方式の容量−電圧変換部（容量検出部）および、ゼロ点・感度調整部により構成される。Ｖｃｃは電源電圧、ＳＷ１，ＳＷ２は切り替えスイッチ、ＣＲは基準容量２００，ＣＳはアクティブ容量１００，ＣＦは作動増幅器Ｇ１のフィードバック容量、Ｇ２は作動増幅器を示す。いまＡ点に下部電極３０ａ−半導体基板１０間の寄生容量があると仮定すると、寄生容量と配線抵抗によりＳＷ１のスイッチング周波数に一次遅れが発生し、測定精度を低下させる。さらに寄生容量が電圧依存性を有する場合、さらに不安定な動作を示し精度が悪化する。Ｂ点に寄生容量が存在する場合、アクティブ容量１００の容量変化量と全容量のＳＮ比が大きくなり測定精度を低下させ、さらに寄生容量が電圧依存性を有すると出力ＶＯが不安定になる。
【００１４】
図１に示した基準容量２００は平行平板型容量でありその容量は電極面積，電極間距離，電極間材料の比誘電率によって決定される。本第一実施例では電極間距離および電極間材料の決定をバリア誘電体層４０によって行っている。バリア誘電体層４０にＣＶＤナイトライド膜を用いた場合、非誘電率は７〜９程度である。このためアクティブ容量１００と比較しほぼ同容量をより小さな面積で達成することができ、このためより安価な圧力センサを提供できる。
【００１５】
第二実施例である図３には、バリア誘電体層４０以外で構成した基準容量２００ の例を示した。本実施例では基準容量２００は、下部電極３０ａ，基準容量誘電体２０１，酸化膜２０２，上部電極６０ａで構成される。本構成では基準容量 ２００の電極間誘電体である基準容量誘電体２０１の厚さ・材料をバリア誘電体層４０とは別個に決定することが出来るため、基準容量２００の面積より小さな圧力センサを安価に提供することができる。
【００１６】
本発明の第３実施例の断面図を図４に、平面図を図５に示す。
【００１７】
本実施例は基準容量２００をアクティブ容量１００と同一の製造方法により製作したものである。基準容量２００は基準容量固定電極３０ｄ，空隙２１０，ダイアフラム構造体２２０で構成され、半導体基板１０上に酸化物誘電体２０を介して形成する。従って、半導体基板１０−基準容量２００間の寄生容量は小さく、実質的に電圧依存性を有さないため、高精度の圧力センサを提供することができる。基準容量２００の固定足場２２０ｂの間隔はアクティブ容量１００の固定足場１２０ｂ間隔に対して十分短く配置しており、周囲圧力に対して実質的に変化しない。例えば、ダイアフラム構造体２２０の変位は固定足場２２０ｂ間隔の４乗に比例するため、固定足場２２０ｂ間隔を固定足場１２０ｂの１／４に設定した場合、容量変化の比は約１／２５６程度となる。
【００１８】
このような構成にすることによって、基準容量固定電極３０ｄはアクティブ容量固定電極３０ｂと、空隙２１０は空隙１１０と、ダイアフラム構造体２２０はダイアフラム構造体１２０と同時に加工することが可能となり、アクティブ容量１００の製造ばらつきを基準容量２００と相殺することができ、さらに同一部材によるためノイズ等の外乱による特性変化も相殺することができる。
【００１９】
本発明の第４実施例の断面図を図６に、平面図を図７に示す。
【００２０】
本実施例はダイアフラム構造体１２０内に基準容量固定電極３０ｄを形成した例である。基準容量固定電極３０ｄは足場１０ｂ近くに配置し、アクティブ容量固定電極３０ｂは中心部に配置する。ダイアフラム構造体１２０の変位は中心部が最大となり固定足場１２０ｂ周辺はほとんど変位しない。このため圧力による基準容量２００の容量変化は実質的に圧力に依存しない。このような構成で面積を最小化した容量式圧力検出部はよく知られているが、半導体基板１０上に検出回路３００と共に集積化する際には、前述した半導体基板１０−基準容量固定電極３０ｄ間の寄生容量が測定精度を悪化させる。このため、本発明では酸化物誘電体２０を介して基準容量固定電極３０ｄを基板上に形成することにより課題の解決をはかった。
【００２１】
以上の様な構成にすることによって、基準容量−半導体基板間の寄生容量を小さくかつ電圧依存性を実質的に無視でき、測定精度の良く、安定した容量式圧力センサを提供することが出来る。
【００２２】
更に、回路部と圧力検出部の１チップ化が可能となり、小型化，低価格化な圧力センサの提供が可能となる。
【００２３】
【発明の効果】
このような構成にすることにより、基準容量−半導体基板間の寄生容量を小さくかつ電圧依存性を実質的に無視でき、測定精度の良く、安定した容量式圧力センサを提供することが出来る。また、回路部と圧力検出部の１チップ化が可能となり、小型化，低価格化な圧力センサの提供が可能となる。さらに、自動車用としても良好な特性で安定した信頼度の高い圧力センサを提供できる。
【図面の簡単な説明】
【図１】本発明の第１実施例の断面形状を示す図。
【図２】本発明の第１実施例の平面図を示す図。
【図３】本発明の第２実施例の断面形状を示す図。
【図４】本発明の第３実施例の断面形状を示す図。
【図５】本発明の第３実施例の平面形状を示す図。
【図６】本発明の第４実施例の平面形状を示す図。
【図７】本発明の第４実施例の断面形状を示す図。
【図８】本発明の圧力検出回路のブロック図を示す図。
【符号の説明】
１０…半導体基板、２０…酸化物誘電体、３０…導電体、３０ａ…下部電極、３０ｂ…アクティブ容量固定電極、３０ｃ…配線、３０ｄ…基準容量固定電極、４０…バリア誘電体層、５０…封止用誘電体、６０…金属導電体、６０ａ…上部電極、６０ｂ…配線部、７０…コンタクト構造、１００…アクティブ容量、１１０ ，２１０…空隙、１２０，２２０…ダイアフラム構造体、１２０ａ，２２０ａ…ダイアフラム電極、１２０ｂ，２２０ｂ…固定足場、１３０…ダイアフラム電極接続部、２００…基準容量、２０１…基準容量誘電体、２０２…酸化膜、２０３…パッシベーション膜、３００…検出回路、４００…圧力検出ＩＣ。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pressure sensor for detecting a pressure of a fluid, and more particularly to a pressure sensor using a semiconductor fine processing technology used for controlling an engine of an automobile.
[0002]
[Prior art]
As a conventional pressure sensor, for example, there is a pressure sensor described in Japanese Patent Application Laid-Open No. 7-6162.
[0003]
The pressure sensor described in Japanese Patent Application Laid-Open No. 7-7162 has a reference capacitance that does not change in response to changes in ambient pressure and a sensing capacitance that changes in response to ambient pressure. A sensor, comprising: a first electrode which is a diffusion layer formed directly on a semiconductor substrate; and a conductive layer made of single-crystal silicon formed to face the first electrode through a cavity sealed to be maintained at a predetermined pressure. It comprises a flexible diaphragm second electrode including a region. A diffusion layer is formed on a semiconductor substrate for both the reference capacitance and the sensing capacitance, and this is used as a first electrode. The sensor described above is characterized in that the flexible diaphragm is displaced by a change in ambient pressure and the capacitance between the first electrode and the second electrode changes correspondingly.
[0004]
[Problems to be solved by the invention]
As a method of increasing the accuracy of a capacitive pressure sensor, as a means for canceling a change in the characteristic of the active capacitance due to a disturbance factor such as processing variation or noise that is not related to a pressure change, a capacitor having a capacity substantially equal to the 2. Description of the Related Art A technique of using a reference electrode which does not substantially change due to pressure and obtaining a difference or a ratio of a change in capacitance between the two by a detection circuit has been well known.
[0005]
A challenge in achieving high accuracy for a capacitive pressure sensor having a reference capacitance, an active capacitance, and a detection circuit on a semiconductor substrate is to adjust the substrate impurity concentration between the reference capacitance and the semiconductor substrate or the potential difference between the substrate and the reference capacitance electrode. That is, a changing parasitic capacitance (junction capacitance) occurs. For this reason, when the semiconductor substrate is connected to a detection circuit that is used as a ground or a power supply voltage, the parasitic capacitance between the electrode and the semiconductor substrate is very large and changes with respect to a predetermined capacitance formed between the electrodes of the reference capacitance, and the active capacitance is changed. There is a problem that the SN ratio of the reference capacitance including the parasitic capacitance with respect to the amount of change in the capacitance increases and changes, and the measurement accuracy decreases.
SUMMARY OF THE INVENTION An object of the present invention is to provide a one-chip pressure sensor that can reduce the parasitic capacitance between the reference capacitance and the semiconductor substrate, substantially neglect the voltage dependency, and have high measurement accuracy.
[0006]
[Means for Solving the Problems]
An object of the present invention is to detect, on a semiconductor substrate, an active capacity that changes according to the ambient pressure, a reference capacity that does not substantially change with respect to the ambient pressure, and a difference or ratio between the active capacity and the reference capacity that is electrically connected to the active capacity and the reference capacity. A circuit that operates using the potential of the semiconductor substrate, wherein the reference capacitor is formed by a conductive electrode provided on the semiconductor substrate via a dielectric, and the semiconductor substrate and the circuit are This is achieved by a connected one-chip semiconductor capacitive pressure sensor.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a sectional view of a first embodiment of the present invention, and FIG.
[0008]
In this embodiment, a pressure detection IC 400 of a semiconductor capacitance type pressure sensor including an active capacitance 100, a reference capacitance 200, and a detection circuit 300 formed on a semiconductor substrate 10 via an oxide dielectric 20 is shown.
[0009]
The semiconductor substrate 10 is a single crystal silicon substrate generally used for a semiconductor. In the case of using a C-MOS device that is known to be highly integrated in fewer steps as compared with a bipolar, an n-type or p-type single crystal CZ substrate having a resistivity of about 8 to 12 Ωcm is used.
[0010]
The oxide dielectric 20 electrically insulates the semiconductor substrate 10 from the active capacitance 100 and the reference capacitance 200 from the semiconductor substrate 10. The oxide dielectric 20 is formed of a thermal oxide film, a CVD (Chemical Vapor Deposition) oxide film, or the like, and has a relative dielectric constant of about 3 to 4. When forming simultaneously with a C-MOS device, a thermal oxide film (field oxide film) can be used, which leads to a reduction in the number of steps, so that a less expensive pressure sensor can be provided.
[0011]
The active capacitance 100 includes an active capacitance fixed electrode 30b, a barrier dielectric layer 40, a void 110, and a diaphragm structure 120. The space 110 is hermetically sealed in a substantially vacuum by the sealing dielectric 50. Therefore, the diaphragm structure 120 is displaced in proportion to the ambient pressure. The diaphragm structure 120 includes a portion of the diaphragm electrode 120a facing the active capacitance fixed electrode 30b and a portion of the fixed scaffold 120b. The diaphragm electrode 120a can be obtained by using polysilicon for the diaphragm structure 120 and conducting it by an impurity diffusion method or the like. The fixed scaffold 120b is fixed to the semiconductor substrate 10 via the barrier dielectric layer 40 by removing the separation layer in advance by using the barrier dielectric layer 40 as an etching stop layer when forming the void 110 by separation layer etching. I can do it. With such a configuration, it is possible to convert a change in ambient pressure as a change in capacitance between the active capacitance fixed electrode 30b and the diaphragm electrode 150. The potentials of the active capacitance fixed electrode 30b and the diaphragm electrode 150 can be led to the detection circuit 300 by the following method. That is, the potential of the diaphragm electrode 150 is guided to the wiring part 60b by the diaphragm electrode connection part 130 via the wiring 30c and the contact structure 70 (FIG. 1). Similarly, the active capacitance fixed electrode 30b reaches the wiring section 60b via the wiring 30c and the contact structure 70 (FIG. 2). The diaphragm electrode connecting portion 130 has a structure in which electrical conduction is obtained by removing a part of the barrier dielectric layer 40 on the wiring 30c formed on the oxide dielectric 20. The lower electrode 30a, the active capacitance fixed electrode 30b, and the wiring 30c are conductive films, and if they are processed simultaneously with the gate of a C-MOS device such as a polysilicon film or a silicide in which impurities are diffused, the process can be simplified and a less expensive pressure sensor can be provided. it can.
[0012]
The reference capacitance 200 includes a lower electrode 30a, a barrier dielectric layer 40, and an upper electrode 60a. The reference capacitor 200 is formed on the semiconductor substrate 10 via the oxide dielectric 20. For this reason, the parasitic capacitance formed between the semiconductor substrate 10 and the lower electrode 30a can be extremely reduced as compared with the conventional example. Furthermore, the parasitic capacitance between the semiconductor substrate 10 and the lower electrode 30a has substantially no voltage dependency. Therefore, a stable pressure sensor with good measurement accuracy can be provided.
[0013]
FIG. 8 shows a block diagram of a pressure sensor to which the present invention is applied. This embodiment includes a general switched capacitor type capacitance-voltage conversion unit (capacitance detection unit) and a zero point / sensitivity adjustment unit. Vcc is a power supply voltage, SW1 and SW2 are changeover switches, CR is a reference capacitance 200, CS is an active capacitance 100, CF is a feedback capacitance of the operational amplifier G1, and G2 is an operational amplifier. Assuming that there is a parasitic capacitance between the lower electrode 30a and the semiconductor substrate 10 at the point A, a first-order lag occurs in the switching frequency of the switch SW1 due to the parasitic capacitance and the wiring resistance, and the measurement accuracy is reduced. Further, when the parasitic capacitance has a voltage dependency, the operation becomes more unstable and the accuracy is deteriorated. When a parasitic capacitance exists at the point B, the capacitance change amount of the active capacitance 100 and the SN ratio of the total capacitance become large, thereby lowering the measurement accuracy. Further, if the parasitic capacitance has voltage dependency, the output VO becomes unstable.
[0014]
The reference capacitance 200 shown in FIG. 1 is a parallel plate capacitance, and its capacitance is determined by the electrode area, the distance between the electrodes, and the relative permittivity of the material between the electrodes. In the first embodiment, the distance between the electrodes and the material between the electrodes are determined by the barrier dielectric layer 40. When a CVD nitride film is used for the barrier dielectric layer 40, the non-dielectric constant is about 7 to 9. For this reason, the same capacitance can be achieved with a smaller area as compared with the active capacitance 100, so that a cheaper pressure sensor can be provided.
[0015]
FIG. 3, which is the second embodiment, shows an example of a reference capacitor 200 constituted by components other than the barrier dielectric layer 40. In the present embodiment, the reference capacitor 200 includes a lower electrode 30a, a reference capacitor dielectric 201, an oxide film 202, and an upper electrode 60a. In this configuration, since the thickness and material of the reference capacitor dielectric 201 which is a dielectric between the electrodes of the reference capacitor 200 can be determined separately from the barrier dielectric layer 40, a pressure sensor smaller than the area of the reference capacitor 200 can be used. It can be provided at low cost.
[0016]
FIG. 4 is a cross-sectional view and FIG. 5 is a plan view of a third embodiment of the present invention.
[0017]
In this embodiment, the reference capacitor 200 is manufactured by the same manufacturing method as the active capacitor 100. The reference capacitor 200 includes a fixed reference capacitor electrode 30d, a gap 210, and a diaphragm structure 220, and is formed on the semiconductor substrate 10 with the oxide dielectric 20 interposed therebetween. Therefore, since the parasitic capacitance between the semiconductor substrate 10 and the reference capacitance 200 is small and has substantially no voltage dependency, a highly accurate pressure sensor can be provided. The distance between the fixed scaffolds 220b of the reference capacity 200 is set to be sufficiently shorter than the distance between the fixed scaffolds 120b of the active capacity 100, and does not substantially change with respect to the ambient pressure. For example, since the displacement of the diaphragm structure 220 is proportional to the fourth power of the interval of the fixed scaffold 220b, when the interval of the fixed scaffold 220b is set to 1/4 of the fixed scaffold 120b, the ratio of the capacitance change is about 1/256. .
[0018]
With this configuration, the fixed reference capacitance electrode 30d can be processed simultaneously with the fixed active capacitance electrode 30b, the gap 210 can be processed with the gap 110, and the diaphragm structure 220 can be processed simultaneously with the diaphragm structure 120. Can be canceled with the reference capacitance 200, and furthermore, the characteristic change due to disturbance such as noise can be canceled because of the same member.
[0019]
FIG. 6 is a sectional view and FIG. 7 is a plan view of a fourth embodiment of the present invention.
[0020]
This embodiment is an example in which a reference capacitance fixed electrode 30 d is formed in the diaphragm structure 120. The fixed reference electrode 30d is disposed near the scaffold 10b, and the fixed reference electrode 30b is disposed at the center. The displacement of the diaphragm structure 120 is maximized at the center and hardly displaces around the fixed scaffold 120b. Therefore, the change in the capacity of the reference capacity 200 due to the pressure does not substantially depend on the pressure. Although a capacitive pressure detector having such a configuration and having a minimized area is well known, when integrated with the detection circuit 300 on the semiconductor substrate 10, the above-described semiconductor substrate 10-reference capacitance fixed electrode 30d The parasitic capacitance between them degrades the measurement accuracy. Therefore, in the present invention, the problem was solved by forming the reference capacitance fixed electrode 30d on the substrate via the oxide dielectric 20.
[0021]
With the above-described configuration, a parasitic capacitance between the reference capacitance and the semiconductor substrate can be reduced, the voltage dependency can be substantially ignored, and a stable capacitive pressure sensor with high measurement accuracy can be provided.
[0022]
Further, the circuit section and the pressure detecting section can be integrated into one chip, and a downsized and low-cost pressure sensor can be provided.
[0023]
【The invention's effect】
With such a configuration, a parasitic capacitance between the reference capacitance and the semiconductor substrate can be reduced and voltage dependency can be substantially ignored, and a stable capacitive pressure sensor with good measurement accuracy can be provided. In addition, the circuit section and the pressure detecting section can be integrated into one chip, and a compact and low-cost pressure sensor can be provided. Further, it is possible to provide a stable and highly reliable pressure sensor having good characteristics even for an automobile.
[Brief description of the drawings]
FIG. 1 is a diagram showing a cross-sectional shape of a first embodiment of the present invention.
FIG. 2 is a plan view of the first embodiment of the present invention.
FIG. 3 is a diagram showing a cross-sectional shape of a second embodiment of the present invention.
FIG. 4 is a diagram showing a cross-sectional shape of a third embodiment of the present invention.
FIG. 5 is a diagram showing a planar shape of a third embodiment of the present invention.
FIG. 6 is a diagram showing a planar shape of a fourth embodiment of the present invention.
FIG. 7 is a diagram showing a cross-sectional shape of a fourth embodiment of the present invention.
FIG. 8 is a block diagram showing a pressure detection circuit according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Semiconductor substrate, 20 ... Oxide dielectric, 30 ... Conductor, 30a ... Lower electrode, 30b ... Active capacitance fixed electrode, 30c ... Wiring, 30d ... Reference capacitance fixed electrode, 40 ... Barrier dielectric layer, 50 ... Sealing Stopping dielectric, 60: metal conductor, 60a: upper electrode, 60b: wiring part, 70: contact structure, 100: active capacity, 110, 210: void, 120, 220: diaphragm structure, 120a, 220a: diaphragm Electrodes, 120b, 220b: fixed scaffold, 130: diaphragm electrode connection, 200: reference capacitance, 201: reference capacitance dielectric, 202: oxide film, 203: passivation film, 300: detection circuit, 400: pressure detection IC.

Claims (5)

半導体基板上に、周囲圧力に応じて変化するアクティブ容量，周囲圧力に対し実質的に変化しない基準容量，前記アクティブ容量および基準容量と電気的に接続され両者の差ないし比を検出し半導体基板の電位を利用して動作する回路を有し、
前記基準容量が、前記半導体基板上に誘電体を介して設けられた導電性の電極によって形成され、
前記半導体基板と前記回路とが接続された１チップの半導体容量式圧力センサ。On the semiconductor substrate, an active capacity that changes according to the ambient pressure, a reference capacity that does not substantially change with respect to the ambient pressure, and a difference or a ratio between the active capacity and the reference capacity that are electrically connected to the active capacity and the reference capacity are detected. A circuit that operates using a potential ,
The reference capacitance is formed by a conductive electrode provided on the semiconductor substrate via a dielectric,
A one-chip semiconductor capacitive pressure sensor in which the semiconductor substrate and the circuit are connected . 請求項１において、
前記基準容量の電極間に誘電体を有することを特徴とする半導体容量式圧力センサ。Oite to claim 1,
A semiconductor capacitance type pressure sensor having a dielectric between electrodes of the reference capacitance . 請求項１において、
前記基準容量の電極間に空隙を有し、前記基準電極の電極および空隙は前記アクティブ容量と同一材料で同時に加工したことを特徴とする半導体容量式圧力センサ。Oite to claim 1,
Has voids between the electrodes of the reference capacitor, electrodes and gaps of the reference electrode is a semiconductor capacitive pressure sensor, characterized in that processed simultaneously in the active volume of the same material. 請求項３において、
前記基準容量の一方の電極は前記アクティブ容量のダイアフラム構造とし、もう一方の電極は前記ダイアフラム構造を前記半導体基板に固定する足場で規定される領域内の前記足場周辺に配したことを特徴とする半導体容量式圧力センサ。Oite to claim 3,
One electrode of the reference capacitor is a diaphragm structure of the active volume, the other electrode, characterized in that arranged on the scaffold around the area defined by scaffold for fixing the diaphragm structure to the semiconductor substrate Semiconductor capacitive pressure sensor. 請求項１から４のいずれかにおいて、
前記アクティブ容量が、前記半導体基板上に前記誘電体を介して設けられたことを特徴とする半導体容量式圧力センサ。In any one of claims 1 to 4,
The semiconductor capacitance type pressure sensor, wherein the active capacitance is provided on the semiconductor substrate via the dielectric.
JP28906198A 1998-10-12 1998-10-12 Capacitive pressure sensor Expired - Lifetime JP3567089B2 (en)

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US09/807,325 US6564643B1 (en) 1998-10-12 1999-09-20 Capacitive pressure sensor
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